Write
There is a trick that a lot of people recommend others to try whenever they have a panic attack, feel stressed, or are full of anxiety. The answer is to get a pen and some paper and write your thoughts down to recollect yourself. It may seem a little bit like a cliche, but for many, it has huge results.
By writing things down on paper, you can in some way, pour your heart and thoughts out and then have the ability to reflect on them later. It is just amazing some of the stuff you thought was a big deal at the time, can seem silly later. It really helps put it all into perspective.